package com.supersystem.utils;

/** 
 * @author luoyegang 
 */  
import java.net.InetAddress;  
import java.net.UnknownHostException;  
import java.security.MessageDigest;  
import java.security.NoSuchAlgorithmException;  
import java.security.SecureRandom;  
import java.util.Random;  
  
public class RandomGUID extends Object {  
   protected final org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory  
      .getLog(getClass());  
  
   public String valueBeforeMD5 = "";  
   public String valueAfterMD5 = "";  
   private static Random myRand;  
   private static SecureRandom mySecureRand;  
  
   private static String s_id;  
   private static final int PAD_BELOW = 0x10;  
   private static final int TWO_BYTES = 0xFF;  
  
   /* 
    * Static block to take care of one time secureRandom seed. 
    * It takes a few seconds to initialize SecureRandom.  You might 
    * want to consider removing this static block or replacing 
    * it with a "time since first loaded" seed to reduce this time. 
    * This block will run only once per JVM instance. 
      */  
  
   static {  
      mySecureRand = new SecureRandom();  
      long secureInitializer = mySecureRand.nextLong();  
      myRand = new Random(secureInitializer);  
      try {  
         s_id = InetAddress.getLocalHost().toString();  
      } catch (UnknownHostException e) {  
         e.printStackTrace();  
      }  
  
   }  
  
  
   /* 
    * Default constructor.  With no specification of security option, 
    * this constructor defaults to lower security, high performance. 
    */  
   public RandomGUID() {  
      getRandomGUID(false);  
   }  
  
   /* 
    * Constructor with security option.  Setting secure true 
    * enables each random number generated to be cryptographically 
    * strong.  Secure false defaults to the standard Random function seeded 
    * with a single cryptographically strong random number. 
    */  
   public RandomGUID(boolean secure) {  
      getRandomGUID(secure);  
   }  
  
   /* 
    * Method to generate the random GUID 
    */  
   private void getRandomGUID(boolean secure) {  
      MessageDigest md5 = null;  
      StringBuffer sbValueBeforeMD5 = new StringBuffer(128);  
  
      try {  
         md5 = MessageDigest.getInstance("MD5");  
      } catch (NoSuchAlgorithmException e) {  
         logger.error("Error: " + e);  
      }  
  
      try {  
         long time = System.currentTimeMillis();  
         long rand = 0;  
  
         if (secure) {  
            rand = mySecureRand.nextLong();  
         } else {  
            rand = myRand.nextLong();  
         }  
         sbValueBeforeMD5.append(s_id);  
         sbValueBeforeMD5.append(":");  
         sbValueBeforeMD5.append(Long.toString(time));  
         sbValueBeforeMD5.append(":");  
         sbValueBeforeMD5.append(Long.toString(rand));  
  
         valueBeforeMD5 = sbValueBeforeMD5.toString();  
         md5.update(valueBeforeMD5.getBytes());  
  
         byte[] array = md5.digest();  
         StringBuffer sb = new StringBuffer(32);  
         for (int j = 0; j < array.length; ++j) {  
            int b = array[j] & TWO_BYTES;  
            if (b < PAD_BELOW)  
               sb.append('0');  
            sb.append(Integer.toHexString(b));  
         }  
  
         valueAfterMD5 = sb.toString();  
  
      } catch (Exception e) {  
         logger.error("Error:" + e);  
      }  
   }  
  
   /* 
    * Convert to the standard format for GUID 
    * (Useful for SQL Server UniqueIdentifiers, etc.) 
    * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6 
    */  
   public String toString() {  
      String raw = valueAfterMD5.toUpperCase();  
      StringBuffer sb = new StringBuffer(64);  
      sb.append(raw.substring(0, 8));  
      sb.append("-");  
      sb.append(raw.substring(8, 12));  
      sb.append("-");  
      sb.append(raw.substring(12, 16));  
      sb.append("-");  
      sb.append(raw.substring(16, 20));  
      sb.append("-");  
      sb.append(raw.substring(20));  
  
      return sb.toString();  
   }  
  
  
     // Demonstraton and self test of class  
     public static void main(String args[]) {  
       for (int i=0; i< 100; i++) {  
         RandomGUID myGUID = new RandomGUID();  
         System.out.println("Seeding String=" + myGUID.valueBeforeMD5);  
         System.out.println("rawGUID=" + myGUID.valueAfterMD5);  
         System.out.println("RandomGUID=" + myGUID.toString());  
       }  
     }  
}  